1. Field of the Invention
The invention relates to a flat picture-reproducing device.
2. Description of the Prior Art
The article entitled "Der flache Fernsehbildschirm" published in Vol. 10 (1980) of the "Funkschau" journal, pp. 63 to 66, FIG. 2, describes such a flat picture-reproducing device. It has a glass faceplate whose inside is coated with phosphor, a digitally addressed control arrangement ("switching stack") for shaping and modulating the stream of electrons, an area cathode which emits a uniform stream of electrons in the direction of the control arrangement, and a metal-shell vacuum enclosure at the rear. The cathode is formed by a periodic array of oxide-coated heating wire. The metal-shell vacuum enclosure serves as a counterelectrode, and a periodic array of field-shaping electrodes is located in a layer between this counterelectrode and the heating wires.
This area cathode requires a large quantity of heat because the cathode has to perform the maximum current density for the peak brightness at any moment, although only a fraction of the current density is needed most of the time. This static operating mode damages the oxide-coated heating wires and shortens their useful life.